School measures up to comp

WHITSUNDAY Anglican School was represented by Jacob Pedersen, Colin Hoyle and Melanie Stevenson in the titration competition in Mackay recently.

The competition was to encourage students who enjoy chemistry – especially practical chemistry – and to recognise those who are becoming proficient.

They competed against 11 other teams from schools in the district and emerged winners on the day.

A merit certificate was awarded to all students who achieve results within 1% of the unknown concentration. All three of our participants were able to do this.

The top two teams are now eligible to enter the finals of the Australian National Chemical Analysis Competition. A more challenging task has to be completed at this level.

What happens in a titration competition is each member of the team starts with a known different concentration of HCl.

Each team member then performs a simple acid-base titration exercise to determine the concentration of their given NaOH. They must titrate accurately to a pale pink (phenolphthalein indicator) end point. Based on this titration they can calculate the concentration of their NaOH. They then perform another titration using the NaOH to determine the “unknown” concentration of acetic acid solution. Titrations can be repeated as many times as solution and time permits. Judging is on the basis of the values the team members report for the acetic acid concentrations.

In order to reduce errors, students need to have a good knowledge and understanding of volumetric analysis, including correct procedures for rinsing various pieces of glassware to prevent contamination errors, knowledge of correct procedures for filling pipettes and burettes and reading volumes of chemicals accurately; patience and a good steady hand for titrating to the light pink indicator end-point of the titration, and knowledge of correct algorithms needed to calculate the unknown concentrations of NaOH and acetic acid from their practical results.

For each member of a team, the difference between their acetic acid concentration and the correct concentration of the acetic acid sample (determined by experienced titrators at each venue) will be calculated. This difference will be squared to give the variance. The team with the lowest sum of variances for the three acetic acid solutions is the winner.